Fire companies utilize pumper trucks to increase the pressure of hydrant water flowing through fire hoses and to pressurized water from drafting tanks. Pumpers draw water through suction valves from sources such as portable water tanks or fire hydrants.
Illustrative of widely used suction inlet valve are the Pre-Con valves available from Hydra-Shield Manufacturing, Inc. of Irving, Tex., covered by U.S. Pat. No. 5,178,185. The Pre-Con valve is designed to operate as an automatic flow control valve which eliminates the need for manual adjustments in reaction to water flow. In hydrant operations, the Pre-Con valve automatically opens in proportion to the flow demand and is capable of automatically balancing flow between multiple water sources. The Pre-Con valve's automatic check valve action also minimizes water hammer. When drafting from a source of water, such as a portable water tank, the check valve action of the Pre-Con valve holds prime water when flow is stopped and allows switching to a booster tank and back to drafting without flow interruption. The Pre-Con valve is an improvement over butterfly valves which it has replaced in many situations.
Pre-Con valves have continued to improve over the years with current configurations having follower-in-slot cam operators rather than external profile cam operators. It has been found that these current configurations have a tendency to freeze in cold weather which can render the valve and associated equipment at least temporarily useless in cold weather.